This invention is in the technical field of detecting the sunken condition of a vehicle in order to improve the safety of the power window function of a vehicle (such as an automobile) and in particular the function of opening the window such that the occupant can escape from a vehicle sunk in water.
Recently, power window systems are coming to be provided with a control circuit for detecting the sunken condition of a vehicle in order to facilitate the escape of occupants dependably from such a vehicle under such a condition. Japanese Patent Publication Tokkai 11-36700, for example, disclosed a technology of preventing a vehicular window from acting on its own will at the time of sinking in water by providing a detection sensor for a sunken condition inside the control box of a power window system such that the relays for driving motors for the windows in both directions will be switched on simultaneously and both terminals of the motor coils will be connected to a power line.
Japanese Patent Publication Tokkai 11-41961 disclosed a device for making vehicular windows dependably operable (at least in the direction of opening them) at the time of sinking into water by providing switching elements (transistors) or switch junctions on both sides of relay coils such that both sides of one of the relay coils corresponding to the operated side are switched on in synchronism when the switch is operated and hence only the specified relay coil will be dependably driven. Since this device does not have the function of detecting whether the vehicle is in a sunken condition or not, it cannot function so as to enable only operations in a specified direction (such as the direction of opening the window) while disabling other operations at the time of a sunken condition or to leave a record of the sunken condition. It is possible, however, to separately provide a device according to aforementioned Japanese Patent Publication Tokkai 11-36700, for example, to detect a sunken condition and to thereupon carry out a suitable corresponding procedure.
Japanese Patent Publications Tokkai 2000-204843, 10-292731 and 11-22301 disclosed the technology of providing a sensor for detecting a sunken condition by detecting water (such as an electrode pair and a float switch for detecting a sunken condition) apart from a control box of a power window system such that the window motor can be driven in the direction of opening the window at the time of a sunken condition for automatically opening the window.
Japanese Patent Publication Tokkai 2000-25542 disclosed the technology of providing not only a water sensor (a first detector) for detecting the contact of water with the vehicular body apart from the control box of the power window system but also a second detector for detecting the contact condition of a tire with the road surface such that a sunken condition will be detected if the first detector indicates the contact of water with the vehicular body and the second detector indicates that the tire is not contacting the road surface and the window is thereupon operated and opened. Regarding this technology, second detectors for detecting suspension stroke, air pressure in the tire, a value related to elongation or contraction of a suspension shock absorber, the oscillation angle of a suspension link or the load on the suspension coil are disclosed.
The technology disclosed in aforementioned Japanese Patent Publication Tokkai 11-36700 is not satisfactory because detection does not take place until the invasion of water into the vehicle makes a certain level of progress after the vehicle falls into water (such as a river, the sea, or flood water) such that the water level reaches the control box. This means that a sunken condition is not always detected sufficiently quickly. Although it may be hoped that power windows can function normally unless the control box is completely immersed in water, there is a high possibility that there may be a leakage elsewhere such that the actuators for the power windows cannot function normally while the control box is still capable of functioning correctly. In short, a sunken condition should be detected as quickly as possible.
By a technology of providing a water-detecting sensor apart from the control box such as disclosed in Japanese Patent Publications Tokkai 2000-204843, 10-292731 and 11-22301, a sunken condition can be detected before the water level reaches the position of the control box if the sensor is appropriately positioned such as the bottom of the vehicular body. To set a sensor apart from the control box, however, complicates the construction and tends to increase the weight of the vehicle. There is also the disadvantage that an extra space for the setting is required and there is the problem of reaching a mistaken conclusion if water is splashed thereupon while the vehicle is running in rain.
Neither is the technology disclosed in Japanese Patent Publication Tokkai 2000-25542 free of problems. Since a sunken condition is not detected unless the tire is found to be in a non-contacting condition with the road surface, the sunken condition may not be detected sufficiently quickly. When the vehicle has fallen into a river where the water is not sufficiently deep or when the level of flood water is only gradually rising from the road surface, for example, a sunken condition should be reported but will not be reported because the tire is not in a non-contacting condition with the road surface. Since a sensor must be set apart from the control box, furthermore, there is the same disadvantage as with the aforementioned technology according to Japanese Patent Publications Tokkai 2000-204843, 10-292731 and 11-22301.